Polymer nanocomposites prepared by incorporating inorganic nano-sized structures into organic polymers have high-performance polymer characteristics which are superior to the characteristics of conventional polymer compositions reinforced by micro-sized structures. This is because of the synergy between the properties of the polymer and the properties of the inorganic structures at the nanoscale level. Other features attributable to polymer nanocomposites include improved thermal resistance, moisture resistance, decreased permeability, charge dissipation and chemical resistance. Most polymer's function effectively below room temperature and so polymer nanocomposites comprising such polymers display good magnetic properties below room temperature. For many applications, there is a need for polymer nanocomposites to perform consistently even at temperatures above room temperature. Generally above room temperature, polymer nanocomposites tend to show paramagnetic properties which are undesirable from a device point of view.
SU-8 is a commercially available UV patternable epoxy based negative photoresist polymer that can be patterned into high aspect ratio structures. It has a very low Young's modulus of about 6 GPa as compared to Si based materials which typically have a Young's modulus of over 100 GPa. SU-8 is therefore a good candidate as structural layer in MicroElectro Mechanical Systems (MEMS). While SU-8 is inherently electrically insulating and non-magnetic, its properties can be modified by the introduction of functional nanostructures into the polymer matrix. Polymer nanocomposites comprising SU-8 embedded with magnetic nickel nanoparticles, carbon black nanoparticles, carbon nanotubes, gold nanoparticles or silver nanoparticles are known for lab-on-a-chip applications. However, such polymer nanocomposites are piezoresistive ie they respond to a change in mechanical conditions through a change in electrical resistance. Hence, the applications of such polymer nanocomposites are limited to systems requiring only unidirectional sensitivity such as sensors.